The FBI in Michigan arrested a man who was trying to purchase grenades and other military explosives to add to an arsenal that could be used for an attack on a building.

Sebastian Zachary Gregerson of Detroit, also known as Abdurrahman Bin Mikaayl, 29, was arrested on Sunday and charged with unregistered possession of a destructive device and unlicensed receipt of explosive materials, reported MLive.com.

The FBI charged in filed court documents on Monday that Gregerson sought to illegally obtain a 40-mm grenade launcher, grenades that could be launched by hand and a Claymore mine, noted MLive.com. Federal agents said the mine contains C-4 and could be exploded remotely.

An undercover agent said Gregerson told him about specific tactics he would use to employ the grenades in an assault on a building, along with how he could make homemade grenades, noted MLive.com.

The Detroit News said the document recounted a 16-month undercover investigation that began when an informant told the FBI that Gregerson was in possession of grenades and bazookas.

The court document said Gregerson started purchasing the items in April 2015, including hundreds of rounds of AK-47 ammunition, tactical gear, ski masks and a training video for using a Russian assault rifle.

According to the FBI, Gregerson allegedly purchased on eBay commercial-grade road spikes that can be used to slow or disable vehicles.

"They're highly illegal, it's a destructive device," Gregerson told the undercover agent, according to court records. "And if you built your own you would have to register them as destructive devices before you built them."

Gregerson is scheduled to appear in U.S. District Court in Detroit on Thursday for a detention hearing, noted MLive.com.

The News reported that a Facebook account belonging to a user with the same name, and the hometown of Dearborn, included an image of a man riding a horse and carrying an Islamic State flag.

"That suggests to me that he is a supporter (of the Islamic State)," Seamus Hughes, deputy director of George Washington University's Program on Extremism, told the News, pointing out that ISIS supporters have used the same photo in the past.